This application is not referenced in any Microfiche Appendix.
Thermoplastic pipe is a popular type of pipe for use in conveying liquids and gases underground. Much of the gas distribution piping now being installed in the United States and many other countries of the world today for underground burial is formed of thermoplastic pipe. An increasing amount of piping for water and sewages is formed of thermoplastic pipe. Thermoplastic pipe has a great advantage when used for conducting gases and liquids, particularly when buried underground since it is inert and therefore not subject to corrosion or galvanic action in the earth as is most metallic piping.
An additional and important advantage of thermoplastic pipe is that lengths of pipe can be easily and effectively joined end-to-end by thermal fusion. For this reason butt-fusion machines have been developed for supporting and joining lengths of plastic in an axial end-to-end relationship. The ends of the pipe are faced and then heated. While in a molten state the ends of two lengths of pipe are axially advanced to engage each other. The engaged pipe is held in position until the molten ends solidify, effectively joining the pipe. This method of joining thermal plastic pipes end-to-end is commonly referred to as xe2x80x9cbutt-fusionxe2x80x9d.
Butt-fusion of thermal plastic pipe is highly effective in that the tensile and bursting pressure strengths of a properly formed joint are usually equal to or greater than the tensile and bursting pressure strengths of the plastic pipe itself. Further, butt-fusion is very economical compared to joining pipe in other ways such as by the use of couplings by which pipe is threaded together or by the use of solvents to weld couplings to plastic pipe. Further, butt-fusion allows pipes of constant diameter to be joined end-to-end without the necessity to enlarge one end of a pipe or reduce the diameter of one end of a pipe to permit it to be joined to an adjacent pipe.
Butt-welding or butt-fusion of plastic pipe is typically carried out employing a machine that has facilities for grasping end portions of first and second lengths of plastic pipe in clamps. After the opposed end portions of two lengths of plastic pipe are grasped by clamps, it is a common procedure to then prepare the end faces of the pipes to be joined so that the ends are each in a plane that is perpendicular the axis of the pipe and therefore so that the ends are parallel to each other. For this purpose, a facer is employed. A facer is a rotatable device having a cutting face on each opposite side. After the pipes are grasp by clamps, the facer is interposed between the opposed ends of the pipes and the pipes are moved one toward the other. In the typical butt-fusion machine, one of the clamped end portions of a length of the pipe is held stationary while the other end portion is moved toward the stationary end. Rather than holding one pipe stationary and moving the opposed adjacent pipe, the system can be operated in which both clamp systems are movable toward each other. Whether one pipe or both pipes are moved the only important action is that the ends to be joined are movable with respect to each other. With a facing machine positioned between opposed ends, the pipes are moved so that the opposed ends of the pipes to be joined simultaneously engage rotating cutters. The cutters shave both opposed ends of the pipes simultaneously to shape the opposed ends so they are in parallel planes and free of voids or irregularities.
After the opposed ends of the pipes have been shaped, the pipes are moved apart from each other to allow the cutter head to be withdrawn.
Next, a heater platen is interposed between the opposed ends of the pipe. A heater platen is a device to heat the ends of the pipes to a temperature in the range of about 375xc2x0 F.-500xc2x0 F. The opposed ends of the pipes are held in contact with the heated platen until the opposed end surfaces reach a molten state. Thereafter the pipes are withdrawn away from each other to allow the heater platen to be removed. The pipes are then immediately moved toward each other without any intervening apparatus so that the molten ends of the pipes abut each other. The pipes are advanced toward each other so that the molten thermoplastic at the ends form an internal and external circumferential bead as the plastic flows as the pipes are forced against each other. The pipes are held in this position a sufficient length of time to allow the molten ends to cool to a temperature that is below the molten statexe2x80x94that is, to cool to a temperature at which the plastic joining the pipes is solid. The pipes are then welded to each other or xe2x80x9cbutt-fusedxe2x80x9d to each other.
The clamps holding the opposed end portions of adjacent length of the pipe can then be removed and the butt-fusion machine then relocated to repeat the procedure as required to initiate a new butt-fusion procedure. By sequentially butt-fusing lengths of pipe, a total integral pipeline of any preselected length can be provided.
For background information relating to butt-fusion of thermoplastic pipe, reference may be had to the following previously issued United States patents:
An improved butt-fusion machine for joining end to end relationship thermal plastic pipes includes an improved indexing system, an improved gland for closing the end of a cylinder piston, a mechanism for simultaneously controlling the position of two valves to thereby allow an operator of a butt-fusion machine to more effectively heat the ends of opposed lengths of plastic pipe and to move the ends while in heated state, in juxtaposed position for fusing the pipe and a circuit for detecting the failure of heating elements in a heating element powered by three phase power source.
The system for effectively joining the opposed ends of two lengths of plastic pipe includes a super-structure for manipulating lengths of the plastic pipe. The super-structure frequently includes a frame having wheels affixed thereto so that the frame and the supporting super-structure can be moved about as required for adjoining lengths of plastic pipe. The super-structure supports a first support shaft and a spaced apart horizontal parallel second support shaft. A first clamp system is supported on the opposed shafts, the first clamp system being arranged to removably grasp an end portion of a first length of plastic pipe. A second clamp system is supported on the support shafts for removably grasping the end portion of a second length of plastic pipe. An actuator system, usually a hydraulic cylinder piston is employed for moving the clamp systems with respect to each other. In a typical arrangement, the first clamp system is maintained stationary on the support shafts while the second clamp system is moved laterally on the support shafts with respect to the first clamp system so that the length of plastic pipe grasped by the second clamp system can be moved toward and away from the first clamp system. However, it can be seen that the butt-fusion machine can be arranged so that both the first and the second clamp systems are movable towards and away from each other.
In order to fuse two lengths of thermal plastic pipe grasped by these support systems that are carried on the opposed support shafts it is necessary to trim the opposed ends of the lengths of plastic pipe so that they are in a common plane, preferably a plane that is perpendicular to the longitudinal axis of the lengths of plastic pipe. This is accomplished by positioning between the opposed lengths of plastic pipe a facer having cutting edges on opposed surfaces. With the facer positioned between the lengths of plastic pipe, the plastic pipes can be moved toward each other to firmly engage the facer. The facer, when energized, rotates to simultaneously shape the opposed ends of the plastic pipes so they will substantially match each other.
After the facing operation is complete, the plastic pipes must be axially separated from each other by moving one of the clamping systems with respect to the other. Once the pipes have been moved apart, the facer system can be withdrawn. To fuse the pipes, the ends of the opposed lengths of pipes must be simultaneously heated so that the opposed ends are concurrently at a molten state. For this purpose, a heater platen is positioned between the opposed lengths of plastic pipe and the lengths of pipe are then moved toward each other to simultaneously engage opposed heated surfaces of the platen. After the ends of the pipes have simultaneously been heated to the molten state, the pipes must be withdrawn away from each other to permit the heater platen to be removed. After the platen is removed, the pipes are moved toward each other in axial alignment to abut their fused end surfaces. The abutted heated end surfaces are held in contacted position for a sufficient length of time to allow the heated surfaces to cool, to a temperature below the molten state, thereby effectively thermally fusing the lengths of pipe to each other.
A properly performed butt-fusion results in the pipes being joined in such a way that the pipes are stronger at the point of fusion than at all unfused portions of the length of the pipes.
The structure that is used to laterally position a facer and a heater platen between opposed ends of plastic pipe and to permit the facer and heater platen to be separately rotated into actuating position and rotated out of actuating position is referred to as xe2x80x9can index carriagexe2x80x9d. An improved system for supporting an index carriage to a butt-fusion machine super-structure that includes a first and second parallel horizontal support shaft makes use of an index shaft that is mounted on the super-structure and spaced from and parallel to the support shafts. An index carriage is slidable on the index shaft. A facer and a heater are separately and pivotally secured to the index carriage. The translation mechanism, which preferably is a piston/cylinder extends from the super-structure to the index carriage to thereby selectively longitudinally locate the index carriage and thereby the facer and heater between the opposed ends of lengths of plastic pipe. A structural beam is secured to the super-structure and parallel to and spaced from the index shaft. The index carriage is slidably secured to the structural beam so that the index carriage is retained in predetermined orientation relative to the horizontal support shafts.
In a preferred arrangement a linear bearing system is mounted on the index shaft to support the index carriage and in a further preferred arrangement the index shaft is designed to support substantially the entire weight of the index carriage including the facer and heater that is supported thereto so that the structural beam functions substantially exclusively to maintain the vertical orientation of the index carriage and specifically the vertical orientation of the facer and heater.
Well designed butt-fusion machines for plastic pipe, including machines for butt-fusion have relatively larger diameter plastic pipes that require the use of cylinder/piston devicesxe2x80x94that is, devices that utilize hydraulic fluid power to attain mechanical force and for moving portions of the butt-fusion machine relative to the machine super-structure. A problem with cylinder pistons is the structure that is used for closing the end of a tubular cylinder having a cylindrical shaft extending from it. The disclosure herein provides the improved structure in the form of a tubular gland having an inner end and an outer end and having an internal shaft receiving opening therethrough, the opening being defined by concentric increased internal diameter portions adjacent the gland inner end and a radially extending fluid port communicating with the increased internal diameter tubular portion. A reduced external diameter at the inner end facilitates receiving the internal tubular surface of a cylinder tube. Adjacent the outer end of the gland is an integral enlarged externally dimensioned flange portion having bolt receiving openings therein that facilitate securing the improved gland structure to the tubular cylinder.
As has been previously stated, butt-fusing opposed ends of plastic pipe by use of a butt-fusion machine requires an operator that has manual dexterity sufficient to control the mechanism such that the lengths of pipe can be moved toward and away from each other and coordinated with the movement of an index mechanism allowing a facer to be inserted and removed, allowing a heater to be inserted and removed and allowing opposed lengths of pipe having ends that have been raised to fusion temperature to be forced into contact with each other and maintained in contact for the time required for fusion to take place. This system requires the manipulation of at least three valves to control the hydraulic action necessary to accomplish a butt-fusion. Since an operator has available only his two hands to control these three valves, the dexterity and coordination of an operator is challenged in order to successfully achieve butt-fusion. To simplify the manual requirements of an operator a mechanism is provided for simultaneously manually controlling two valves by the use of one hand. This mechanism employs valve spools that are vertically positioned adjacent to each other and includes a manually controllable pivot memberxe2x80x94that is, pivotal for left and right. A first lug extends laterally from the pivot member and a first horizontal direction and a second lug extends laterally from the pivot member in a second horizontal direction, the second lug being rotatably spaced 90xc2x0 from the first lug. A first positioning member is affixed to the first valve spool and has a horizontally extending opening receiving the first lug, a second positioning member is affixed to the second spool and has an opening receiving the second lug. At least one of the openings in a positioning member is preferably elongated allowing a lug to move laterally in the positioning member without vertically changing the positioning member so that the lug can move laterally without either opening or closing the valve to which the positioning member is attached. The single mechanism thereby which preferably has an elongated handle affixed to the pivot member allows an operator the use of one hand to control two valves to either open or close each of them separately or to open and/or close both valves simultaneously, all with one hand.
An important piece of equipment necessary for achieving highest quality butt-fusion of plastic pipes is the heater, sometimes referred to as a heater platen. A heater is employed in butt-fusing plastic pipe is a plate having opposed surfaces, the plate being typically circular and having embedded in the plate electric resistance heating elements. Electrical energy is supplied to the heating elements to raise the opposed surfaces of the heater platen to a temperature that will relatively quickly raise the opposed ends of plastic pipes to molten temperature. While the energy requirements for fusing the ends of small diameter plastic pipes is not great, fusing large diameter plastic pipes such as twelve inches or greater requires substantial electrical energy, particularly where the objective is to quickly heat the ends of the plastic pipe so as to speed up the butt-fusion process. For this reason, it is a common practice in the industry to power the heater platens for butt-fusion machines for larger diameter pipe with three phase energy. That is, the heater elements embedded within the heater are connected to receive three phase energy meaning that typically the heater elements are connected in either a wye or delta configuration. If a heater element fed by a three phase power source failsxe2x80x94that is, burns out or develops an open circuit, the electrical energy supplied to the other two phases of the three phase circuitry can continue to heat a portion of the heater elements within a platen. This results in uneven heating of the platen that can result in defective butt-fusion. The system herein provides a circuit for detecting the failure of a heating element in a three phase wye or delta arrangement fed by three phase power source by employing current transformers that measure the current flow through each of the three conductors extending from the three phase power source. A current imbalance sensor is connected to the three current transformers to provide a circuit change when unbalance is detected between the level of current sensed by the three current transformers. An indicator, preferably an indicator light or sound generator such as a horn, is actuated by the current imbalance sensor to provide a warning to an operator that a fault has occurred in the heaters employed in a heater platen.